Optimal Volume, Rate, and Interval of Bolus Nerve Catheters for Shoulder Surgery

The purpose of this study is to determine the ideal delivery of local anesthetics for
postoperative analgesia when using continuous interscalene peripheral nerve catheters for
shoulder surgery. New technology has emerged with electronic pumps that permit intermittent
mandatory boluses of local anesthetic to be delivered in addition to continuous infusions.
The pump would automatically deliver a bolus at a given interval, but would otherwise be idle
for a period of time. This technology could improve the efficacy of local anesthetics, and
thereby improve postoperative analgesia.

Continuous peripheral nerve catheters have been shown to improve pain control in several
orthopedic surgical procedures when compared to opioids. However, it is not uncommon for
patients to experience breakthrough pain in spite of a functional peripheral nerve block.
Many times, this breakthrough pain can be managed with a bolus of local anesthetic
administered by an anesthesia provider. Until recently, the vast majority of peripheral nerve
catheter infusion pumps have only had the capability of providing a constant rate of local
anesthetic administration. Newer technology allows for infusion pumps to deliver intermittent
mandatory boluses of local anesthetic. This technique of local anesthetic administration has
previously been evaluated with popliteal nerve blocks, but to our knowledge has never been
evaluated for use with interscalene nerve catheters.

Currently, data would support the idea that a bolus of local anesthetic can improve analgesia
with decreased side effects compared to a continuous infusion. However, there is little data
evaluating the optimal volume of bolus, the optimal speed of delivery, or the optimal
interval between local anesthetic boluses.

Inclusion Criteria:

- Male or female, ≥18 years of age

- Patients scheduled to undergo unilateral shoulder surgery at Duke University Medical
Center, including arthroscopic rotator cuff repair, acromioplasty, hemiarthroplasty,
and total shoulder replacement.

- American Society of Anesthesiology (ASA) Physical Class 1-3.

- BMI ≤40 kg/m2

Exclusion Criteria:

- Patients with a contraindication to placement of interscalene nerve block. This
includes abnormal clotting, skin infection involving the neck, the presence of
neurological disorders or cervical spine disease, contralateral phrenic nerve
dysfunction, or moderate-severe COPD (FEV1<80% of normal values and/or FEV1/FVC <
0.70)

- Patients with chronic pain (pain existing for longer than 6 months), or taking chronic
opioids (greater than 60 morphine equivalents per day) at time of surgery

- Contraindications to or known drug interactions with local anesthetics

- Patients who will be discharged home directly from PACU

- Planned administration of another investigational product or procedure during the
subject's participation in this study.

- Patients who do not have the capacity to give legally effective consent

- Suspected, or known addiction to or abuse of illicit drug(s), prescription
medicine(s), or alcohol within the past 2 years.

- Uncontrolled anxiety, schizophrenia, or other psychiatric disorder that, in the
opinion of the Investigator, may interfere with study assessments or compliance.

- Current or historical evidence of any clinically significant disease or condition
that, in the opinion of the Investigator, may increase the risk of surgery or
complicate the subject's postoperative course.

- Pregnant women